This invention relates to an induction type (more specifically variable reluctance type) rotational position detection device having primary and secondary windings provided on the stator side and no windings on the rotor side and, more particularly, to a rotational position detection device capable of producing change in the coefficient of induction by using eddy current loss as a parameter. This invention further relates to a rotational position detection device capable of producing an enhanced change in the coefficient of induction by using both reluctance change (permeance change) and eddy current loss as parameters thereby realizing a high-precision detection.
As an induction type rotational position detection device of a type having primary and secondary windings provided on the stator side and no windings on the rotor side, there is known a rotary type differential transformer called microsyn which produces an output signal having a voltage level responsive to a rotational position. There is also known a detection device as disclosed in Japanese Preliminary Patent Publication No. 70406/1982 which is of a type outputting an AC signal having an electrical phase angle corresponding to the rotational position. Such prior art detection devices realize change in the coefficient of induction in a coil in response only to reluctance change (permeance change) caused by displacement of a magnetic substance member.
Due to this construction, accuracy of detection in these prior art devices is limited. Further, magnetic substance material must be processed into a predetermined shape to produce a rotor and this requires a complicated processing work. Besides, since the rotor is made by machining work, reduction in size and cost is also limited.